Without restart or modification of config, nginx is sending incomplete responses sometimes. Today, I could reproduce well, but still don't know what's wrong or how to fix.
I put a 5MB file to the site's location/alias path that nginx is configured to use. There is no php5-fpm, modules etc. only nginx for serving static files.
When testing, there is no other user accessing the server, no http access except my test requests.
The download fails and Google Chrome shows in traffic log, that there were 2 requests, although I put the http url for the download only ONCE and there was no redirect or other 2nd request initiated by myself.
Same issue at server's access.log, too:
TEST1
[14/May/2014:14:06:53 +0200] "GET /dev/test_test.m4v HTTP/1.1" 206 1 "-" "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/32.0.1700.107 Safari/537.36"
[14/May/2014:14:06:53 +0200] "GET /dev/test_test.m4v HTTP/1.1" 200 130680 "-" "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/32.0.1700.10
[14/May/2014:14:07:15 +0200] "GET /dev/test_test.m4v HTTP/1.1" 206 1 "-" "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/32.0.1700.107 Safari/537.36"
[14/May/2014:14:07:15 +0200] "GET /dev/test_test.m4v HTTP/1.1" 200 114684 "-" "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/32.0.1700.10
You can see that theere is always one request with response size=1 and another one with mixed size, but >1. However, the result in the browser is always the same. => broken response, failed download.
For making sure, it's not related to http status/response 206, I add max_ranges 0; to the config and retry -> test2.
TEST2
[14/May/2014:14:11:36 +0200] "GET /dev/test_test.m4v HTTP/1.1" 200 152460 "-" "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/32.0.1700.107 Safari/537.36"
[14/May/2014:14:11:38 +0200] "GET /dev/test_test.m4v HTTP/1.1" 200 142296 "-" "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/32.0.1700.107 Safari/537.36"
Same result in the browser. Always failed download/request and the size in access.log is always different, like random chunk or response size.
server status: iowait, RAM, cpu are almost idle. There is no high load or limitation.
Is this a known issue or bug or do You know how to fix this?
With a scenario as simple as this, I'm pretty sure you have a firewall, IDS/IPS device or something else in front of your nginx server disturbing downloads. If in doubt, contact your ISP.